CN110304041B

CN110304041B - Vehicle and control method of vehicle

Info

Publication number: CN110304041B
Application number: CN201910212860.4A
Authority: CN
Inventors: 佐佐木启介; 植田启仁
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2018-03-22
Filing date: 2019-03-20
Publication date: 2022-05-06
Anticipated expiration: 2039-03-20
Also published as: RU2019106153A; RU2735702C2; US10710573B2; JP2019167846A; RU2019106153A3; CN110304041A; EP3543054A1; BR102019004545A2; KR20190111782A; JP6881366B2; KR102183178B1; US20190293000A1

Abstract

The invention relates to a vehicle and a control method of the vehicle. A vehicle includes an internal combustion engine, a catalyst provided in an exhaust passage of the internal combustion engine, and an electronic control unit. The electronic control unit is configured to, when changing an engine torque generated by the internal combustion engine, make a 1 st torque change amount of the engine torque when a temperature of the catalyst belongs to a predetermined low temperature region smaller than a 2 nd torque change amount of the engine torque when the temperature of the catalyst belongs to a high temperature region. The high temperature region is a region higher in temperature than the low temperature region.

Description

Vehicle and control method of vehicle

Technical Field

The present invention relates to a control system of a vehicle, and more particularly, to a vehicle having an engine and a control method of the vehicle.

Background

Japanese patent laid-open No. 2014-210566 discloses a control system of a hybrid vehicle having an engine and a running motor. In this control system, when the catalyst warm-up request is made, the engine output is controlled so as to be a constant engine output. This makes it possible to bring the operating point of the engine close to an operating region where fuel efficiency is good, and therefore, fuel efficiency during catalyst preheating can be improved.

Disclosure of Invention

However, the above-described conventional techniques have the following problems. That is, even if the output of the engine is controlled to be constant, the engine torque generated by the engine fluctuates during this period. When engine torque fluctuates sharply during warming up of the catalyst, the air-fuel ratio fluctuates, and the emission characteristics of the exhaust gas may deteriorate.

The present invention suppresses deterioration of emission characteristics of exhaust gas even during warming up of a catalyst in a vehicle equipped with an internal combustion engine.

The invention according to claim 1 is a vehicle. The vehicle includes an internal combustion engine, a catalyst provided in an exhaust passage of the internal combustion engine, and an electronic control unit. The electronic control unit is configured to control the engine torque such that a 1 st torque variation amount of the engine torque is smaller than a 2 nd torque variation amount of the engine torque. The 1 st torque variation is a torque variation when the temperature of the catalyst belongs to a predetermined low temperature region, and the 2 nd torque variation is a torque variation when the temperature of the catalyst belongs to a high temperature region. The high temperature region is a region having a higher temperature than the low temperature region.

According to the above configuration, when the temperature of the catalyst belongs to the low temperature region, the torque variation amount of the engine torque is smaller than that in the case of belonging to the high temperature region. This can suppress the fluctuation of the air-fuel ratio when the temperature of the catalyst falls within the low temperature range, and therefore can suppress the deterioration of the emission characteristics of the exhaust gas.

The vehicle may further include an electric motor coupled to the wheel via a power transmission mechanism, and a battery that stores electric power for driving the electric motor. The electronic control unit may be configured to control the engine torque and a motor torque transmitted from the electric motor to the wheels based on a required driving force required by the vehicle.

According to the above configuration, the vehicle is equipped with the internal combustion engine and the electric motor driven by the battery. Therefore, according to the above configuration, the engine torque generated by the internal combustion engine and the motor torque transmitted to the wheels by the electric motor can be controlled, and therefore, the torque control can be optimized according to the situation.

In the vehicle, the electronic control unit may be configured to supplement, by the motor torque, a torque insufficient by the engine torque so that the driving force of the vehicle approaches the driving force demand, when the temperature of the catalyst belongs to the low temperature region.

According to the above configuration, when the temperature of the catalyst falls within the low temperature range, the shortage of the required driving force is supplemented by the motor torque. Thus, even when the amount of torque change in the engine torque is small, the driving force of the vehicle can be brought close to the required driving force.

In the vehicle, the electronic control unit may be configured to control the engine torque so that the 1 st torque variation amount of the engine torque when the temperature of the catalyst is lower than a predetermined determination temperature is smaller than the 2 nd torque variation amount of the engine torque when the temperature of the catalyst is higher than the predetermined determination temperature, when the engine torque is varied.

According to the above configuration, the amount of torque change during warming up of the catalyst is smaller than the amount of torque change after completion of warming up of the catalyst. This makes it possible to suppress variation in the air-fuel ratio during warming up of the catalyst having low purification performance and to improve the responsiveness of the engine torque after completion of warming up of the catalyst.

In the vehicle, the electronic control unit may be configured to increase the 1 st torque change amount of the engine torque as the temperature of the catalyst increases when the temperature of the catalyst is lower than the predetermined determination temperature when the engine torque is changed.

According to the above configuration, the amount of torque change in warming up the catalyst increases as the catalyst temperature increases. This makes it possible to increase the amount of torque change in accordance with the improvement in the purification performance of the catalyst, and therefore, it is possible to suppress the deterioration of the emission characteristics of the exhaust gas and optimize the torque response.

In the vehicle, the electronic control unit may be configured to, when changing the engine torque, control the engine torque such that a 1 st torque change amount of the engine torque during a predetermined period from a cold start of the internal combustion engine until a predetermined determination time elapses is smaller than a 2 nd torque change amount of the engine torque after the predetermined determination time elapses.

The elapsed time from the cold start is an index of the degree of warming up of the catalyst. Therefore, according to the above configuration, deterioration of the emission characteristic of the exhaust gas can be suppressed by controlling the amount of torque change using the elapsed time from the cold start.

In the vehicle, the electronic control unit may be configured to gradually increase the 1 st torque variation amount of the engine torque during the predetermined period when the engine torque is varied.

According to the above configuration, the amount of change in torque of the elapsed time from the cold start increases as the catalyst temperature increases. This can increase the amount of torque change in accordance with the improvement in the purification performance of the catalyst, and therefore, the deterioration of the exhaust emission characteristics and the optimization of the torque response can be achieved.

The 2 nd aspect of the invention is a control method of a vehicle. The vehicle includes an internal combustion engine, a catalyst provided in an exhaust passage of the internal combustion engine, and an electronic control unit. The control method comprises the following steps: controlling, by the electronic control unit, the engine torque so that a 1 st torque variation amount of the engine torque is smaller than a 2 nd torque variation amount of the engine torque. The 1 st torque variation amount is a torque variation amount when the temperature of the catalyst belongs to a predetermined low temperature region. The 2 nd torque variation amount is a torque variation amount when the temperature of the catalyst belongs to a high temperature region. The high temperature region is a region higher in temperature than the low temperature region.

Drawings

Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein like reference numerals refer to like parts.

Fig. 1 is a diagram showing a configuration of a vehicle control system according to embodiment 1.

Fig. 2 is a timing chart showing an operation of torque control in catalyst warming-up of a comparative example.

Fig. 3 is a timing chart showing an operation of torque control in catalyst warming-up according to embodiment 1.

Fig. 4 is a graph showing the relationship between the catalyst temperature and the torque rate.

Fig. 5 is a flowchart showing a routine for torque control executed by the control device of embodiment 1.

Fig. 6 is a diagram showing a modification of the method of setting the torque rate according to embodiment 1.

Fig. 7 is a diagram showing a relationship between elapsed time from cold start of the engine and the torque rate.

Fig. 8 is a flowchart showing a routine for torque control executed by the control device of embodiment 2.

Fig. 9 is a diagram showing a modification of the method of setting the torque rate according to embodiment 2.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in the case where numerical values such as the number, the quantity, the amount, the range, and the like of each element are mentioned in the embodiments shown below, the mentioned numerical values do not limit the present invention unless the numerical values are specifically indicated or clearly specified in principle. In addition, the structures, steps, and the like described in the embodiments shown below are not essential to the present invention, unless otherwise explicitly indicated or clearly specified in principle.

Fig. 1 is a diagram showing a configuration of a vehicle control system according to embodiment 1. A vehicle 1 shown in fig. 1 is a power split (split) hybrid vehicle having a plurality of power units. In more detail, the vehicle 1 has an engine 2 as 1 power unit for driving the wheels 14 to rotate. The engine 2 is an internal combustion engine that outputs power by combustion of a hydrocarbon fuel such as gasoline or light oil (diesel oil), and includes an intake device, an exhaust device, a fuel injection device, an ignition device, a cooling device, and the like. A catalyst 32 for purifying exhaust gas is provided in an exhaust passage 30 constituting an exhaust device. The catalyst 32 is provided with a temperature sensor 34 for detecting the catalyst temperature.

The vehicle 1 has a 1 st motor generator 4 and a 2 nd motor generator 6 as motors capable of generating electric power as another power device for driving the wheels 14 to rotate. The 1 st motor generator 4 and the 2 nd motor generator 6 are ac synchronous type generator motors having both a function as a motor that outputs torque from supplied electric power and a function as a generator that converts input mechanical power into electric power. The 1 st motor generator 4 mainly functions as a generator, and the 2 nd motor generator 6 mainly functions as a motor.

The engine 2, the 1 st motor generator 4, and the 2 nd motor generator 6 are coupled to wheels 14 via a power transmission mechanism 8. The power transmission mechanism 8 includes a power distribution mechanism 10 and a reduction mechanism 12. The power split mechanism 10 is, for example, a planetary gear unit, and divides the torque output from the engine 2 into the 1 st motor generator 4 and the wheels 14. The torque output from the engine 2 or the torque output from the 2 nd motor generator 6 is transmitted to the wheels 14 via the speed reduction mechanism 12.

The 1 st motor generator 4 regeneratively generates electric power by the torque supplied through the power split mechanism 10. In a state where no torque is output from the engine 2 and the 2 nd motor generator 6, the 1 st motor generator 4 regenerates electric power, whereby a regenerative braking force is transmitted from the 1 st motor generator 4 to the wheels 14 via the power transmission mechanism 8, and the vehicle 1 decelerates. That is, the vehicle 1 can perform regenerative braking with the 1 st motor generator 4.

The 1 st motor generator 4 and the 2 nd motor generator 6 exchange electric power with the battery 16 via an inverter (inverter)18 and a converter (converter) 20. The inverter 18 is designed to be able to consume the electric power generated by one of the 1 st motor generator 4 and the 2 nd motor generator 6 at the other. The inverter 18 converts the electric power stored in the battery 16 from a direct current to an alternating current and supplies the converted electric power to the 2 nd motor generator 6, and also converts the electric power generated by the 1 st motor generator 4 from an alternating current to a direct current and stores the converted electric power in the battery 16. Therefore, the battery 16 is charged with the electric power generated by either one of the 1 st motor generator 4 and the 2 nd motor generator 6 or discharged with the electric power insufficient for either one.

The vehicle 1 includes a control device 50 that controls the operations of the engine 2, the 1 st motor generator 4, the 2 nd motor generator 6, the power split mechanism 10, and the like to control the traveling of the vehicle 1. The Control device 50 is an ECU (Electronic Control Unit) having at least 1 processor and at least 1 memory. The memory stores various programs for running control of the vehicle 1, and various data including maps. The control device 50 can implement various functions by the processor executing the program stored in the memory. The control device 50 performs control of the intake air amount, fuel injection control, ignition timing control, and the like of the engine 2. The control device 50 also performs power running control for causing the 1 st motor generator 4 and the 2 nd motor generator 6 to function as motors, and regenerative control for causing them to function as generators. Further, the control device 50 may be configured by a plurality of ECUs.

The control device 50 performs acquisition processing of signals of sensors included in the vehicle 1. The sensors are installed at various places of the vehicle 1. The vehicle 1 is equipped with a rotation speed sensor 52 for detecting the rotation speed of the crankshaft, an accelerator position sensor 54 for outputting a signal corresponding to the amount of depression of the accelerator pedal as the accelerator opening, a vehicle speed sensor 56 for detecting the vehicle speed, and the like, in addition to the temperature sensor 34. In addition, although many sensors are connected to the control device 50 in addition to those shown in the drawings, the description thereof will be omitted in this specification. The control device 50 executes various programs using the acquired sensor signals, and outputs operation signals for operating the actuators.

The control of the vehicle 1 by the control device 50 includes torque control for controlling the torque transmitted to the wheels 14. In the torque control here, the engine torque Te and the motor torque Tm are controlled so that the torque transmitted to the wheels 14 becomes the required driving force.

The engine torque Te is a torque generated by the engine 2. The control device 50 performs intake air amount control, fuel injection control, and ignition timing control of the engine 2 so that the engine torque Te becomes the target engine torque.

The motor torque Tm is a torque transmitted from the 1 st motor-generator 4 or the 2 nd motor-generator 6 to the wheels 14. The motor torque Tm is mainly constituted by the torque output from the 2 nd motor generator 6. However, there are also cases where: at the time of deceleration at which the regenerative braking force of the 1 st motor generator 4 is transmitted to the wheels 14, the motor torque Tm includes a negative torque output from the 1 st motor generator 4. The control device 50 performs power running control and regeneration control of the 1 st motor generator 4 and the 2 nd motor generator 6 so that the motor torque Tm becomes the target motor torque.

Here, torque control of the vehicle 1 has a problem that exhaust emission characteristics deteriorate during warm-up of the catalyst 32. That is, the purification performance of the catalyst 32 is low during a period in which the catalyst 32 does not reach the activation temperature, for example, immediately after a cold start of the engine 2. When the transient operation of the engine 2 is performed during the catalyst warming-up, the air-fuel ratio fluctuates and the exhaust emission characteristic deteriorates.

Here, in order to clarify the problem of the torque control, 1 comparative example is given. Fig. 2 is a timing chart showing an operation of torque control in catalyst warming-up of a comparative example. In fig. 2, the graph of the layer 1 shows the temporal change in the vehicle speed of the vehicle, the graph of the layer 2 shows the temporal change in the accelerator opening degree, the graph of the layer 3 shows the temporal change in the engine torque Te, the graph of the layer 4 shows the temporal change in the motor torque Tm, the graph of the layer 5 shows the temporal change in the air-fuel ratio, and the graph of the layer 6 shows the temporal change in the exhaust emission.

In the comparative example shown in fig. 2, a case is exemplified in which the driver depresses the accelerator pedal at time t1 during the catalyst warming, and a sudden acceleration of the vehicle is requested. When the accelerator opening degree is changed to the increasing side, the engine torque Te and the motor torque Tm are respectively changed to the increasing side to achieve the required driving force corresponding to the accelerator opening degree. When the engine torque Te rises sharply, the air-fuel ratio fluctuates once along with this and the exhaust gas flow rate increases. In the comparative example shown in fig. 2, the catalyst 32 is in the warming-up state, so the exhaust emission characteristic deteriorates under the influence of the fluctuation of the air-fuel ratio and the increase of the exhaust gas flow rate.

In the torque control according to embodiment 1, the above problem is solved by limiting the amount of change in torque of the engine torque Te during catalyst warming (hereinafter, also referred to as "torque rate"). Hereinafter, the torque control according to embodiment 1 will be described in more detail with reference to fig. 3.

Fig. 3 is a timing chart showing an operation of torque control in catalyst warming-up according to embodiment 1. In fig. 3, the graph of the layer 1 shows the temporal change in the vehicle speed of the vehicle, the graph of the layer 2 shows the temporal change in the accelerator opening degree, the graph of the layer 3 shows the temporal change in the engine torque Te, the graph of the layer 4 shows the temporal change in the motor torque Tm, the graph of the layer 5 shows the temporal change in the air-fuel ratio, and the graph of the layer 6 shows the temporal change in the exhaust emission.

As shown in fig. 3, in the torque control of embodiment 1, the torque rate when the engine torque Te is changed is set to be smaller than that in the comparative example. According to such torque control, in the transient operation in which the engine torque Te is changing, the effect of suppressing the fluctuation of the air-fuel ratio and the effect of reducing the exhaust gas flow rate can be obtained as compared with the case of the comparative example. This suppresses an increase in exhaust emission, and therefore, the emission characteristics can be improved.

From the viewpoint of improving the responsiveness of the engine torque Te, the torque rate is desirably increased as much as possible while suppressing the deterioration of the exhaust emission as much as possible. Then, in the torque control of embodiment 1, the torque rate is set in accordance with the catalyst temperature. Fig. 4 is a graph showing the relationship between the catalyst temperature and the torque rate. As shown in this figure, the torque rate can be set to a value that is larger as the catalyst temperature is higher, for example. According to such setting of the torque rate, the torque rate when the catalyst temperature belongs to a predetermined low temperature region is set to be smaller than the torque rate when the catalyst temperature belongs to a high temperature region higher than the low temperature region. As the catalyst temperature becomes high, the purification performance of the catalyst 32 improves. Therefore, according to the above-described setting of the torque rate, the torque rate can be increased as the purification performance of the catalyst 32 improves. This can suppress deterioration of the exhaust emission characteristics and optimize improvement of the torque responsiveness of the engine torque Te.

Further, as shown in fig. 3, when the torque rate is set smaller than that in the case of the comparative example, the engine torque Te during the transient operation is reduced accordingly. Therefore, in the torque control of embodiment 1, it is desirable to adopt a control configuration in which the amount of decrease in the engine torque Te is supplemented by the motor torque Tm. In the graph shown in fig. 3, the motor torque Tm is set such that the total value of the engine torque Te and the motor torque Tm approaches the required driving force during the transient operation from time t1 to time t2, at which the engine torque Te changes. Thus, the motor torque Tm during the transient operation becomes a larger value than in the case of the comparative example. According to such control, the torque insufficient for the required driving force can be supplemented by the increase of the motor torque Tm. Thus, even in a state where the purification performance of the catalyst is low, the torque output by the vehicle 1 can be made close to the required driving force while suppressing deterioration of the exhaust emission characteristic.

Fig. 5 is a flowchart showing a routine for torque control executed by the control device 50 according to embodiment 1. The processor of the control device 50 executes the program shown in the flowchart at predetermined cycles. Hereinafter, the contents of the torque control of embodiment 1 will be described with reference to a flowchart.

In the flowchart shown in fig. 5, first, the required driving force required by the driver for the vehicle 1 is calculated based on the accelerator opening degree or the like detected by the accelerator position sensor 54 (step S100). Then, a required output for realizing the required driving force is calculated based on the required driving force calculated in step S100 and the vehicle speed detected by the vehicle speed sensor 56 (step S102).

Next, a vehicle request output requested by the vehicle 1 is calculated (step S104). Here, a value obtained by adding a charge/discharge request output determined by a charge/discharge request of the battery 16 to the request output is calculated as a vehicle request output. Then, a target engine output for achieving the vehicle required output is calculated based on the output ratios of the engine 2 and the 1 st and 2 nd motor generators 4 and 6 (step S106). Then, the target engine rotational speed is calculated (step S108). The memory of the control device 50 stores a map that defines the relationship among the engine rotational speed, the engine torque, the engine output, and the optimum fuel consumption rate. Here, using this map, the engine rotational speed at which the target engine output is achieved based on the optimal fuel consumption rate is calculated as the target engine rotational speed.

Subsequently, a torque rate is calculated (step S110). Specifically, the catalyst temperature is first detected by the temperature sensor 34. Then, the torque rate corresponding to the detected catalyst temperature is calculated from the relationship between the catalyst temperature and the torque rate shown in fig. 4.

Next, a target engine torque is calculated as a target value of the engine torque Te using the calculated torque rate (step S112). Then, the target engine torque is subtracted from the required driving force to calculate a target motor torque as a target value of the motor torque Tm (step S114).

By performing torque control using the target engine torque, the target engine rotational speed, and the target motor torque calculated in the above-described procedure, torque control according to the purification performance of the catalyst 32 can be performed. Thus, since the torque rate when the purification performance of the catalyst 32 is low is set small, deterioration of the exhaust emission characteristic can be suppressed.

The present invention is not limited to embodiment 1 described above, and the following modifications can be adopted within the scope not departing from the gist of the present invention.

In embodiment 1, a hybrid vehicle of a power split system in which torques from the engine 2 and the 1 st and 2 nd motor generators 4 and 6 can be freely combined or divided has been described as an example. However, the vehicle 1 to which the control system of embodiment 1 is applied may be a vehicle adopting another hybrid system. For example, the vehicle 1 may be a so-called parallel hybrid vehicle in which a plurality of power sources including an engine are used for driving wheels. The vehicle 1 may be a so-called series hybrid vehicle in which the engine is used only for power generation and the motor generator is used for driving and regenerating the wheels. This modification can also be applied to the control system of embodiment 2 described later.

The vehicle 1 to which the control system of embodiment 1 is applied is not limited to a hybrid vehicle. That is, the vehicle 1 may be a vehicle equipped with only the engine 2 as a power unit for rotationally driving the wheels 14. This modification can also be applied to the control system of embodiment 2 described later.

The catalyst temperature of the catalyst 32 is not limited to the configuration detected by the temperature sensor 34. That is, the catalyst temperature may also be the temperature of the exhaust gas on the downstream side of the catalyst 32. The catalyst temperature may be estimated by a known method from the operating state of the engine 2.

The torque control of embodiment 1 is not limited to be executed when a torque increase request is made to the vehicle, and may be executed when a torque decrease request is made. That is, for example, when a torque reduction request is issued during catalyst warm-up, a situation is considered in which fuel cut is not performed due to other control requests such as catalyst warm-up control. In this case, by reducing the amount of change in the engine torque Te to the reduction side, the fluctuation of the air-fuel ratio can be suppressed. In this case, the 1 st motor/generator 4 may generate the negative motor torque Tm by regenerative control, and the torque transmitted to the axle may be controlled so as to approach the required driving force. This modification can also be applied to the control system of embodiment 2 described later.

The calculation of the torque rate is not limited to the method using the relationship shown in fig. 4. Fig. 6 is a diagram showing a modification of the method of setting the torque rate according to embodiment 1. In modification 1-1 shown in the figure, the torque rate is fixed to a predetermined 1 st torque rate value in a low temperature region until the catalyst temperature reaches the determination temperature, and when the catalyst temperature exceeds the determination temperature and shifts to a high temperature region, the torque rate is switched from the predetermined 1 st torque rate value to a 2 nd torque rate value larger than the 1 st torque rate value. The determination temperature can be set to, for example, an activation temperature of the catalyst 32. According to such control, the torque rate can be reduced before the activity of the catalyst 32 is exhibited, deterioration of exhaust emission can be suppressed, and the torque rate can be increased after the activity of the catalyst 32 is exhibited, thereby improving the responsiveness of the engine torque Te.

In modification 1-2 shown in fig. 6, the torque rate is increased in stages in accordance with the increase in the catalyst temperature until the catalyst temperature reaches the determination temperature. According to such control, the torque rate before the activity of the catalyst 32 is exhibited can be set stepwise according to the catalyst temperature. This makes it possible to improve the responsiveness of the engine torque Te in stages while suppressing deterioration of exhaust emission.

In modification 1-3 shown in fig. 6, the torque rate is continuously increased in accordance with the increase in the catalyst temperature until the catalyst temperature reaches the determination temperature. According to such control, the torque rate before the activity of the catalyst 32 is exhibited can be continuously set according to the catalyst temperature. This can continuously improve the responsiveness of the engine torque Te while suppressing deterioration of exhaust emission.

Next, embodiment 2 will be explained. The control system according to embodiment 2 can be realized by employing the hardware configuration shown in fig. 1 and causing the control device 50 to execute the routine shown in fig. 8 described later.

In the torque control of embodiment 1 described above, the torque rate is set in accordance with the catalyst temperature. In contrast, the torque control according to embodiment 2 is characterized by the following operations: the torque rate is set according to the elapsed time from the cold start of the engine 2.

At the time of cold start of the engine 2, the catalyst temperature gradually increases with the passage of time, and eventually reaches the activation temperature. Therefore, the catalyst temperature until the elapsed time reaches the predetermined determination time is lower than the catalyst temperature after the elapse of the determination time. In other words, the catalyst temperature belongs to a low temperature region until the elapsed time reaches a predetermined determination time, and after the determination time has elapsed, the catalyst temperature belongs to a high temperature region higher than the low temperature region.

Then, in the torque control of embodiment 2, the torque rate is set in accordance with the elapsed time from the cold start of the engine 2. Fig. 7 is a diagram showing a relationship between elapsed time from cold start of the engine and the torque rate. As shown in this figure, in the torque control of embodiment 2, the torque rate is fixed to the predetermined 1 st torque rate value until the elapsed time from the cold start of the engine 2 reaches the predetermined determination time, and when the elapsed time exceeds the determination time, the torque rate is switched from the predetermined 1 st torque rate value to the 2 nd torque rate value larger than the 1 st torque rate value. The determination time may be a value obtained in advance through an experiment or the like as an elapsed time from the cold start to completion of warming up of the catalyst 32, for example. According to such torque control, the torque rate can be reduced before the activity of the catalyst 32 is exhibited, deterioration of exhaust emission can be suppressed, and the torque rate can be increased after the activity of the catalyst 32 is exhibited, thereby improving the responsiveness of the engine torque Te.

Fig. 8 is a flowchart showing a routine for torque control executed by the control device 50 according to embodiment 2. The processor of the control device 50 executes the routine shown in the flowchart at a predetermined cycle when the engine 2 is cold-started. Hereinafter, the contents of the torque control of embodiment 2 will be described with reference to a flowchart.

In steps S200 to S208 of the routine shown in fig. 8, the same processing as in steps S100 to S108 shown in fig. 5 is performed. After the process of step S208 is performed, it is next determined whether the elapsed time from the cold start of the engine 2 reaches a predetermined determination time (step S210). As a result, when it is determined that the determination is not satisfied, it is determined that the warming-up of the catalyst 32 is not completed, and the target engine torque is calculated based on the 1 st torque rate value (step S212). On the other hand, when the determination is considered to be established, it is determined that the warm-up of the catalyst 32 is completed, and the target engine torque is calculated based on the 2 nd torque rate value larger than the 1 st torque rate value (step S214).

After the processing of step S212 or step S214 is performed, the target motor torque is calculated by subtracting the target engine torque from the required driving force (step S216).

By performing torque control using the target engine torque, the target engine rotational speed, and the target motor torque calculated in the above-described procedure, it is possible to perform torque control according to the purification performance of the catalyst 32 without detecting the catalyst temperature. Thus, since the torque rate when the purification performance of the catalyst 32 is low is set small, deterioration of the exhaust emission characteristic can be suppressed.

The present invention is not limited to embodiment 2 described above, and the following modifications can be made without departing from the scope of the present invention.

The calculation of the torque rate is not limited to the method using the relationship shown in fig. 7. Fig. 9 is a diagram showing a modification of the method of setting the torque rate according to embodiment 2. In modification 2-1 shown in fig. 9, the torque rate is increased in stages in accordance with the increase in the catalyst temperature until the elapsed time becomes the determination time. According to such control, the torque rate before the activity of the catalyst 32 is exhibited can be set stepwise according to the catalyst temperature. This makes it possible to improve the responsiveness of the engine torque Te in stages while suppressing deterioration of exhaust emission.

In modification 2-2 shown in fig. 9, the torque rate is continuously increased in accordance with the increase in the catalyst temperature until the catalyst temperature reaches the determination temperature. According to such control, the torque rate before the activity of the catalyst 32 is exhibited can be continuously set according to the catalyst temperature. This can continuously improve the responsiveness of the engine torque Te while suppressing deterioration of exhaust emission.

Claims

1. A vehicle, characterized by comprising: an internal combustion engine, a catalyst provided in an exhaust passage of the internal combustion engine, and an electronic control unit,

the electronic control unit is configured to control the engine torque such that a 1 st torque variation amount of the engine torque is smaller than a 2 nd torque variation amount of the engine torque;

the 1 st torque variation amount is a torque variation amount when the temperature of the catalyst belongs to a predetermined low temperature region, the 2 nd torque variation amount is a torque variation amount when the temperature of the catalyst belongs to a high temperature region, and the high temperature region is a region higher in temperature than the low temperature region;

the electronic control unit is further configured to increase the 1 st torque variation amount of the engine torque as the temperature of the catalyst increases when the temperature of the catalyst is in the predetermined low temperature region.

2. The vehicle of claim 1, further comprising: a motor coupled to a wheel via a power transmission mechanism, and a battery that stores electric power for driving the motor;

the electronic control unit is configured to control the engine torque and a motor torque transmitted from the electric motor to the wheels based on a required driving force required by the vehicle.

3. The vehicle according to claim 2, wherein the vehicle is a hybrid vehicle,

the electronic control unit is configured to supplement, by the motor torque, a torque insufficient by the engine torque so that the driving force of the vehicle approaches the required driving force when the temperature of the catalyst belongs to the low temperature region.

4. The vehicle according to any one of claims 1 to 3,

the electronic control unit is configured to make the 1 st torque variation amount of the engine torque when the temperature of the catalyst is lower than a predetermined determination temperature smaller than the 2 nd torque variation amount of the engine torque when the temperature of the catalyst is higher than the predetermined determination temperature.

5. The vehicle according to any one of claims 1 to 3,

the electronic control unit is configured to make a 1 st torque variation amount of the engine torque in a predetermined period from a cold start of the internal combustion engine until a predetermined determination time elapses smaller than a 2 nd torque variation amount of the engine torque after the predetermined determination time elapses.

6. The vehicle according to claim 5, wherein the vehicle is a hybrid vehicle,

the electronic control unit is configured to gradually increase the 1 st torque variation amount of the engine torque during the predetermined period.

7. A method for controlling a vehicle, comprising the steps of,

the vehicle includes: an internal combustion engine, a catalyst provided in an exhaust passage of the internal combustion engine, and an electronic control unit,

the control method is characterized by comprising:

controlling, by the electronic control unit, an engine torque such that a 1 st torque variation amount of the engine torque is smaller than a 2 nd torque variation amount of the engine torque;

the 1 st torque variation amount is a torque variation amount when a temperature of the catalyst belongs to a predetermined low temperature region, the 2 nd torque variation amount is a torque variation amount when the temperature of the catalyst belongs to a high temperature region, and the high temperature region is a region higher in temperature than the low temperature region;

the control method further comprises the following steps: causing, by the electronic control unit, the 1 st torque variation amount of the engine torque to increase as the temperature of the catalyst increases when the temperature of the catalyst is in the predetermined low temperature region.